Improvement in adjustable electro-magnets for relays



T. A. EDISON.

Adjustable Electra-Magnet for Relays, 8m.

N() ]6(),4()5, PatentedMarch2,I875.

THE GRAPHIG:C0.PHOTU:LITH.39 3.41 PARK PLACEJLY.

UNITED STATES PATENT OFFICE.

THOMAS A. EDISON, OF NEWARK, NEW JERSEY, ASSIGNOR TO HIMSELF AND GEORGEHARRINGTON, OF WASHINGTON, D. G.

IMPROVEMENT lN ADJUSTABLE ELECTRO-MAGNETS FOR RELAYS, &c.

Specification forming part of Letters Patent No. 160,405, dated March 2,1875 application filed July 29, 1873.

To all whom it may concern Be it known that I, THOMAS A. EDISON, of ofNewark, in the county of Essex and State of New Jersey, have invented anImprovevement in Adjusting Electro-Magnets, of which the following is aspecification:

'With an electro-magnet employed for a sounder or receiving-instrumentit is very difficult to adjust the action, because the intensity of thecurrent varies greatly, and frequently false currents reach the magnetand prevent its proper action. To provide for these variouscircumstances, it is usual either to vary the tension of the retractilespring, or adjust the position of the armature and core in relation toeach other.

My invention is made with reference to obtainin g a uniformity ofcurrent in the electromagnet, and avoiding the adjustment of the magnetor the parts thereof. I make use of a shunt or branch circuit connectedat both sides of the electro-magnet, and in that shunt I place aregulator composed of several helices or resistance-coils connected toeach other and to circuit-pins, and employ an arm that can be revolvedupon a center and bring into the shunt greater or less resistance, andthereby directing the proper proportion of the current through theeleetro-magnet and allowing the remainder to pass through the shunt.

In the drawing, Figure 1 is a side view of the electro-magnet, and Fig.2 is a plan of the shunt-regulator.

The electro-magnet a is of ordinary character, and employed as a sounderor otherwise.

The shunt-regulator contains the resistancecoils b I), connected to eachother through the circuit-pins c e in the center of which is the pivot dof the arm a. The line f is connected through the magnet a and by theshunt-wires g with the pivot cl and first coil 1).

If the arm 0 is turned so as only to include one coil 1) in the shunt,the resistance will be but little, and most of the current will pass bythe shunt and but little through the electromagnet to, and by turningthis arm 6 any desired number of coils I) will be included in the shunt,so that, as the resistance increases, so the proportion of currentdirected through the magnet a will increase also.

1 do not claim a rheostat or adjustable resistance in a shunt-circuit,to regulate the current passing through a chemical receiving-instrument.I do not claim a shunt around an electro-magnet with a resistance thatis not variable and serves to lessen the injury to the contact-points.

I claim as my invention- The variable resistance I), placed in ashuntcircuit, in combination with an electro-magnet for equalizingaction of the current in the electro-magnet and dispensing with thespringadjustment, as set forth.

Signed by me this 23d day of April, A. D. 1873.

THOS. A. EDISON.

Witnesses:

GEo. T. PINGKNEY, OnAs. H. SMITH.

